There are a variety of applications in which a data file is transferred from a data transferring unit to a target storage device in order to have the data file copied onto the target storage device. These applications include peer-to-peer remote copy (PPRC) systems, storage area network (SAN) systems, and systems generally having memory or a host connected to a target storage device. In these applications similar data files may be stored on the target storage device. This is a problem because it is not efficient to store multiple copies of similar data files on the target storage device because each data file may need a large amount of storage space even though the differences between the data files may be slight. Delta difference data is indicative of the differences between two data files. That is, a second data file may be determined by merging a first data file with delta difference data indicative of the differences between the first and second data files. Typically, the delta difference data takes up much less storage space than a data file.